This reminds me of a great April Fools prank to play on my fellow Mac users:

System Preferences > Universal Access > Seeing > Display: use grayscale

It's more subtle than plain inverted colours, and the kind of thing that might make someone think their monitor is dying.

Unfortunately in the process of loading the pictures came up in color before the JS managed to filter them to greyscale :(.

It was actually a good bit of work to pull this off, replacing the color in everything site wide... We may write it up in case it is actually useful to somebody out there.

Maybe you could reuse this code to preview how a color scheme would look through the eyes of a color-blind. Or through a color-blind filtering software.

I mean it was definitely very cool, just too bad it wasn't quite seamless.

Brilliant! This is the sort of April Fool's Prank we need far more of.